How are BioLegend's carrier-free recombinant proteins shipped?


Our carrier-free recombinant proteins are shipped on blue ice.  These products have been validated to maintain activity after shipping using blue ice.  


What is a carrier protein?


Carrier proteins, such as BSA, improve the stability of the reconstituted protein, and helps prevent the product from sticking to the wall of the vial.


What is the difference between the carrier-free and the non carrier-free recombinant proteins?


All our carrier-free and animal-free formats of recombinant proteins do not have any additional carrier proteins such as BSA in the formulation. Typically our ELISA standard recombinants have carrier proteins added to the formulation for added stability and to avoid the product from sticking to the wall of the vial. When the presence of carrier is not desirable (e.g., in-vivo applications), carrier-free proteins can be used directly. When carrier proteins do not affect the outcome in a study, the customer can decide what type of carrier protein they would like to use and whether it is necessary to add it to their stock.


Can I use different recombinant proteins from different companies for my ELISA?


Antibodies used are different in different kits. The specificity of the antibodies partially dictate how much signal is being detected. Recombinant standards used are different. First of all, different kits may use recombinant proteins expressed and purified using different method. Second, recombinant proteins expressed from E. coli from the same source can show greater than 10 fold difference in term of immunoreactivity from lot to lot, primarily due to refolding inconsistency. Third, different kit standards can be produced and calibrated against different references. So far there is no universally accepted standardization for cytokine immunoreactivities. Each BioLgend ELISA product was developed and validated with reagent concentrations and protocols optimized for best analytical robustness. Any changes to the reagents (standards, antibodies, matching matrices) and protocols etc all affect the final assay performance.


How does the activity of your recombinant proteins compare to competitors?


We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!


What is the specific activity or ED50 of my recombinant protein?


The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet.


What should I reconstitute the protein with? What do you recommend for its long-term storage?


Most of our carrier-free recombinants are shipped in liquid form, so there is no need for reconstitution. Our animal-free recombinant proteins are shipped in lyophilized form and protein reconstitution information is indicated on the respective datasheets. If you need to make dilutions, refer to the formulation on the product data sheet. Stock solutions should be prepared at 50-100 μg/mL in buffer containing carrier protein such as 1% BSA or HSA or 10% FBS (for chemokines, use either BSA or HSA). For long-term storage, aliquot into polypropylene vials and store in a manual defrost freezer. Avoid repeated freeze/thaw cycles.

For reconstitution of our lyophilized recombinant proteins (ELISA Std, animal-free, and some carrier-free) please refer to the Certificate of Analysis and/or Technical Datasheet included with the product and follow the instructions. 


Are BioLegend’s recombinant proteins suitable for in vitro and in vivo bioassays?


BioLegend’s recombinant protein solutions are 0.2 μm-filtered prior to bottling by membrane filtration method. In addition, our recombinants are endotoxin-tested and are guaranteed to have levels less than 0.1 ng per μg protein. All our recombinants can be safely used for both in vitro and in vivo bioassays.


Do you test the bioactivity of your recombinant proteins with in vivo assays?


We typically validate the activity of the proteins with in-vitro assays as described on the data sheet and not with in-vivo testing. However, all our carrier-free and animal-free formats can be used for in vivo applications as is evident from many customers who have successfully used it for this purpose.


Does specific activity of a recombinant protein vary between lots?


Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.


What is the difference between laboratory (observed) units and international units?


There is no direct relationship between International Units and the units that are calculated using the inverse of the specific activity because we do not use the International Standard provided by WHO (National Institute for Biological Standards and control). The best way to compare the activity of two sources of recombinants is by doing the bioassay side by side using the same system.


How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?


Use the formula Specific activity (Units/mg) = 106/ ED50 (ng/mL)


Have your recombinants been tested for stability?


Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.


What is the difference between carrier-free and animal-free categories of recombinant proteins?


Our animal-free products are proteins that go through the entire production process without touching any animal containing components. This includes using animal-free media and purification equipment that are animal component-free. Some studies which are particularly sensitive to contamination by mammalian pathogens may require the use of animal-free products. Our carrier-free products do not contain any carrier protein in the solution, as expected, but they are produced using animal-containing components. Both versions are expected to have similar activity and function, though specific activity is lot-dependent.